1. Degradation of Ester Lubricants Department of Chemistry John R. Lindsay Smith, Edward D. Pritchard, Moray S. Stark,* David J. Waddington Department of Chemistry, University of York York, YO10 5DD, UK

2. Degradation of Ester Lubricants Part 2: The Oxidation of Polyol Esters John R. Lindsay Smith, Edward D. Pritchard, Moray S. Stark,* David J. Waddington Department of Chemistry, University of York York, YO10 5DD, UK mss1@york.ac.uk www.york.ac.uk/res/gkg

3. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate Department of Chemistry

4. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate Model Compounds neopentyl hexanoate Department of Chemistry

5. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoate Model Compounds

6. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoate TMP tributanoate Model Compounds

7. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoateTMP trihexanoate TMP tributanoate Model Compounds

8. Oxidation of Ester Lubricants Reactor Steel : BS 316 PTFE Stirrer Conditions 160 ºC 0.5 cm 3 lubricant 4.4 cm 3, 5 barA Oxygen Department of Chemistry

9. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoateTMP trihexanoate TMP tributanoate Model Compounds

10. Oxidation of Neopentylglycol Dibutanoate : GC Trace time (min) GC: Supelcowax, 30 m, 0.25 mm ID, 0.25  m,FID

11. time (min) Oxidation of NPG Dibutanoate : Main Products

12. time (min) Oxidation of NPG Dibutanoate : Diol Formation

13. Oxidation of NPG Dibutanoate : Hydroxyesters time (min)

14. Oxidation of NPG Dibutanoate : Esters of Hydroxyesters time (min)

15. Oxidation of NPG Dibutanoate : α,β-Unsaturated Ester time (min)

16. Formation of α,β-Unsaturated Ester Department of Chemistry

17. Formation of α,β-Unsaturated Ester Department of Chemistry

18. Formation of α,β-Unsaturated Ester Department of Chemistry

19. Oxidation of NPG Dibutanoate : Cyclic Acetal time (min)

20. Formation of Cyclic Acetals Department of Chemistry

21. Formation of Cyclic Acetals Department of Chemistry

22. Formation of Cyclic Acetals Department of Chemistry

23. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoateTMP trihexanoate TMP tributanoate Model Compounds

24. Oxidation of TMP Tributanoate : GC Trace

25. Oxidation of TMP Tributanoate : Main Products Butanoic acid TMP Dibutanoate

26. Oxidation of TMP Tributanoate : Transesterification TMP Dibutanoate monomethanoate TMP Dibutanoate monoethanoate TMP Dibutanoate monopropanoate eg. methyl butanoate

27. Oxidation of TMP Tributanoate : Oxidation Products

28. Oxidation of TMP Tributanoate : Cyclic Acetal

29. Main Products of TMP Tributanoate Oxidation Department of Chemistry

30. Main Products of TMP Tributanoate Oxidation Department of Chemistry

31. Transesterification Products

32. Transesterification Products : II Department of Chemistry

33. Possible Hydrolysis of TMP Tributanoate? Department of Chemistry

34. Water Content During Autoxidation Department of Chemistry

35. Water Content During Autoxidation Department of Chemistry

36. TMP Tributanoate Oxidation : Viscosity Increase

37. Viscosity Increase : Correlation with TMP Dibutanoate

39. Formation of High Molecular Weight Species mass : 344 mass 430 458 516 530 544 610 630 Department of Chemistry

40. Formation of High Molecular Weight Species : II oxidation + esterification (-H 2 O) mass : 344 mass : 430 radical attack (+ O 2 - O) (+ RH)

41. Formation of High Molecular Weight Species : III oxidation mass : 344 mass : 458 radical attack + cleavage + (+ O 2 - O)

42. Formation of High Molecular Weight Species : IV oxidation + (-H 2 O) mass : 344 mass : 544 radical attack esterification

43. Trimethylolpropane (TMP) Esters lubricant base fluid : TMP tridodecanoate neopentylglycol dibutanoateTMP trihexanoate TMP tributanoate Model Compounds

44. TMP Trihexanoate vs. TMP Tributanoate Oxidation

46. Conclusions : Main Oxidation Mechanisms of Polyol Esters Department of Chemistry

47. Conclusions : Main Oxidation Mechanisms of Polyol Esters Polyol Esters can decompose to the Diol and form Cyclic Acetals Department of Chemistry

48. Conclusions : Main Oxidation Mechanisms of Polyol Esters Polyol Esters can decompose to the Diol and form Cyclic Acetals Triol Ester decomposition dominated by Hydrolysis- Transesterification Department of Chemistry

49. Conclusions : Main Oxidation Mechanisms of Polyol Esters Polyol Esters can decompose to the Diol and form Cyclic Acetals Triol Ester decomposition dominated by Hydrolysis- Transesterification High molecular weight species formed by esterification of alcohol oxidation products Department of Chemistry

50. Conclusions : Main Oxidation Mechanisms of Polyol Esters Polyol Esters can decompose to the Diol and form Cyclic Acetals Triol Ester decomposition dominated by Hydrolysis- Transesterification High molecular weight species formed by esterification of alcohol oxidation products Acknowledgements Peter Smith and Castrol Department of Chemistry

51. Abstract for STLE Conference : Toronto, 17-20 th May 2004 Degradation of Ester Lubricants: Part 2: The Oxidation of Polyol Esters John R. Lindsay Smith, Edward D. Pritchard, Moray S. Stark*, David J. Waddington Department of Chemistry, University of York, York, YO10 5DD, UKe-mail: mss1@york.ac.uk Abstract for STLE Conference, Toronto, May 2004, Lubricant Fundamentals Section The oxidation mechanisms of the polyol ester lubricant, trimethylolpropane (TMP) tridodecanoate, and representative chemical models (neopentylglycol dibutanoate, TMP tributanoate, TMP trihexanoate) have been studied. The esters of mono-alcohols are known to decompose mainly via oxidation reactions, analogous to those of alkanes. However, for diol and triol esters, following initial oxidation, the degradation is dominated by hydrolysis and transesterification, with the acid formed by loss of the acyl group being the major product. Two previously unreported degradation/polymerisation mechanisms of polyol esters have also been observed. These involve reactions with aldehydes (primary oxidation products) to form cyclic acetals and, if the acid group is sufficiently long, the oxidation of the acid chain to an alcohol followed by the formation of lactones, via attack of the hydroxyl group on the ester linkage. The results from these studies are important in the search for improved stability of polyol ester lubricants.